Bone fractures are very common. The National Health Interview Survey (1985-1988) showed an average annual incidence of 1.4 million persons with long bone fractures. The National Ambulatory Medical Care Survey indicated 3.5 million long bone fractures in 1985.
When a bone fracture occurs, the bone is usually displaced from its original alignment. This may occur in a number of ways, which are described in the following section.
Types of Bone Fractures
When a bone is fractured, the displacement of the bone from the original alignment typically takes one or more of the following forms: shortening or overlapping, rotation, lateral shift, angulation, and/or separation. The two segments of the broken bone are referred to as the proximal end and the distal end, with the proximal end being that which is closest to the heart. In general, the proximal end is held fixed while the distal end is moved to match the proximal segment for the actual reduction.
When shortening or overlapping occurs, the bone ends overlap each other, and the length of the broken bone is shorter than that of an unfractured bone.
Rotation occurs when the distal bone segment rotates along its longitudinal axis. When this happens, the diameter and contour of the fractured bone ends will not generally be equal.
A lateral shift refers to a displacement of the bone ends perpendicular to the bone's longitudinal axis by some shift distance.
Angulation occurs when the broken bone ends no longer form the same angle as that of an unbroken bone.
Finally, and most rarely, separation occurs when the fractured ends are separated and are apart from each other in a direction parallel to the bone's longitudinal axis. It occasionally happens as the result of a traction procedure.
Treatment of Bone Fractures
The repair of a broken bone generally involves the processes of reduction, immobilization and fixation, and physical therapy. Reduction refers to the technique whereby the broken bone ends are brought back into alignment. Once reduced, the fracture undergoes immobilization and fixation, which stabilize the reduced fracture during the healing process. Immobilization includes casting, splinting, and bracing of a stable fracture. Fixation includes closed and open internal fixation, and external fixation for unstable fractures. Finally, physical therapy recovers the functions of the limbs after the reduction and immobilization/fixation are completed.
Previous and current methods of setting such fractures are replete with limitations. For example, if the medical team sets the fracture while a fluoroscope monitors progress, the medical team is exposed to certain amounts of x-ray radiation, even despite the use of heavy leaded aprons. Such exposure has been shown to induce aplastic anemia, leukemia, other solid malignant tumors, and inhibition of the reproductive function.
If a fluoroscope is not used, a series of x-ray films must be taken and repeated manual reductions may be needed to secure a proper alignment. This creates a high risk of additional damage to surrounding vessels, nerves, and soft tissues with possible complications to patients, such as mal-union, non-union, paralysis, or ischemia syndrome.
Another limitation is the practical difficulty of immobilizing a bone fracture and applying a cast or splint while at the same time holding the bone ends in alignment. This is particularly true as full recovery of the limb's function requires almost perfect reduction, which in turn requires the physician's manual dexterity to be accurate to within a few millimeters.
A further limitation with current systems is the use of one-plane x-ray films or fluoroscopic views. Such images do not allow the physician to accurately estimate the three-dimensional displacements of the fracture. For example, a physician often has to make an incision into a limb to directly observe the reduction. This additional damage to the patient may result in complications such as infections, delayed unions, non-unions, and other soft tissue injuries.
A still further limitation is the dependence of the success of the fracture reduction on the individual physician's strength, skill, sensitivity, and experience, all of which may vary widely.
Finally, it is worth noting the heavy labor-intensiveness of current systems for bone reduction. In particular, a physician is required as well as at least two assistants. Also, an anesthesiologist and an x-ray technician are necessary.
Systems that provide mechanisms for assisting physicians in bone procedures have been described in the prior art. As an example, U.S. Pat. Nos. 4,979,949, 5,154,171, and 5,236,432, all issued to Matsen III et al., include controller-driven robots which control tools used for bone operations. However, these patents do not describe a system which can grasp and manipulate the bone itself. Additionally, they do not include fluoroscopes for continuous monitoring of the status of the bone, nor do they include types of safeguards, such as limb tension monitoring and automatic cessation of reduction procedures, as does the present invention.
U.S. Pat. Nos. 4,558,697, 5,013,317, 4,485,815, and 4,471,768 are also directed towards bone grips or other devices. However, they are deficient for even more reasons, such as reduced accuracy or the need for physician exposure to the x-ray beam.
There is a need for an x-ray based orthopedic surgical robot that can, with great accuracy, reduce fractures of bones such as these: radius, ulna, humerus, tibia, fibula, and femur. There is further a need for a system which can allow a physician to monitor the x-ray image outside the x-ray shield and operate a remote control to direct a robot to reduce the bone fracture using the robot's hands. This would minimize the exposure of physicians to excessive radiation as well as provide a convenient holding block for limbs while the fracture is immobilized via a cast or splint. There is still further a need for a system which can give the physician precise information on the three-dimensional displacements of the fractured bones. Such a system may even provide the physician with suggestions on what steps should be taken to reduce the fracture. Finally, there is a need for a bone reduction system which reduces the dependence on individual physicians' skill and experience, while at the same time also reducing the overall number of professionals needed during the reduction operation.